This invention concerns effector proteins of Rapamycin. More particularly, this invention concerns novel Rapamycin-FKBP12 binding proteins of mammalian origin for identification, design and synthesis of immunomodulatory, anti-restenosis or anti-tumor agents.
Rapamycin is a macrolide antibiotic produced by Streptomyces hygroscopicus which was first characterized via its properties as an antifungal agent. It adversely affects the growth of fungi such as Candida albicans and Microsporum gypseum. Rapamycin, its preparation and its antibiotic activity were described in U.S. Pat. No. 3,929,992, issued Dec. 30, 1975 to Surendra Sehgal et al. In 1977 Martel, R. R. et al. reported on immunosuppressive properties of rapamycin against experimental allergic encephalitis and adjuvant arthritis in the Canadian Journal of Physiological Pharmacology, 55, 48-51 (1977). In 1989, Calne, R. Y. et al. in Lancet, 1989, no. 2, p. 227 and Morris, R. E. and Meiser, B. M. in Medicinal Science Research, 1989, No. 17, P. 609-10, separately reported on the effectiveness of rapamycin in inhibiting rejection in vivo in allograft transplantation. Numerous articles have followed describing the immunosuppressive and rejection inhibiting properties of rapamycin, and clinical investigation has begun for the use of rapamycin in inhibiting rejection in transplantation in man.
Rapamycin alone (U.S. Pat. No. 4,885,171) or in combination with picibanil (U.S. Pat. No. 4,401,653) has been shown to have antitumor activity. R. R. Martel et al. [Can. J. Physiol. Pharmacol. 55, 48 (1977)] disclosed that rapamycin is effective in the experimental allergic encephalomyelitis model, a model for multiple sclerosis; in the adjuvant arthritis model, a model for rheumatoid arthritis; and effectively inhibited the formation of IgE-like antibodies.
The immunosuppressive effects of rapamycin have been disclosed in FASEB 3, 3411 (1989). Cyclosporin A and FK-506, other macrocyclic molecules, also have been shown to be effective as immunosuppressive agents, therefore useful in preventing transplant rejection [FASEB 3, 3411 (1989); FASEB 3, 5256 (1989); R. Y. Calne et al., Lancet 1183 (1978); and U.S. Pat. No. 5,100,899].
Rapamycin has also been shown to be useful in preventing or treating systemic lupus erythematosus [U.S. Pat. No. 5,078,999], pulmonary inflammation [U.S. Pat. No. 5,080,899], insulin dependent diabetes mellitus [Fifth Int. Conf. Inflamm. Res. Assoc. 121 (Abstract), (1990)], and smooth muscle cell proliferation and intimal thickening following vascular injury [Morris, R. J. Heart Lung Transplant 11 (pt. 2): 197 (1992)].
Mono- and diacylated derivatives of rapamycin (esterified at the 28 and 43 positions) have been shown to be useful as antifungal agents (U.S. Pat. No. 4,316,885) and used to make water soluble prodrugs of rapamycin (U.S. Pat. No. 4,650,803). Recently, the numbering convention for rapamycin has been changed; therefore according to Chemical Abstracts nomenclature, the esters described above would be at the 31- and 42-positions. U.S. Pat. No. 5,118,678 discloses carbamates of rapamycin that are useful as immunosuppressive, anti-inflammatory, antifungal, and antitumor agents. U.S. Pat. No. 5,100,883 discloses fluorinated esters of rapamycin. U.S. Pat. No. 5,118,677 discloses amide esters of rapamycin. U.S. Pat. No. 5,130,307 discloses aminoesters of rapamycin. U.S. Pat. No. 5,117,203 discloses sulfonates and sulfamates of rapamycin. U.S. Pat. No. 5,194,447 discloses sulfonylcarbamates of rapamycin.
U.S. Pat. No. 5,100,899 (Calne) discloses methods of inhibiting transplant rejection in mammals using rapamycin and derivatives and prodrugs thereof. Other chemotherapeutic agents listed for use with rapamycin are azathioprine, corticosteroids, cyclosporin (and cyclosporin A), and FK-506, or any combination thereof.
Rapamycin produces immunosuppressive effects by blocking intracellular signal transduction. Rapamycin appears to interfere with a calcium independent signalling cascade in T cells and mast cells [Schreiber et al. (1992) Tetrahedron 48:2545-2558]. Rapamycin has been shown to bind to certain immunophilins which are members of the FK-506 binding proteins (FKBP) family. In particular, Rapamycin has been shown to bind to the binding proteins, FKBP12, FKBP13, FKBP25 [Galat A. et al., (1992) Biochemistry 31(8);2427-2437 and Ferrera A, et al., (1992) Gene 113(1):125-127; Armistead and Harding, Ann. Reports in Med. Chem. 28:207-215, 1993], and FKBP52 [WO 93/07269]
Rapamycin is able to inhibit mitogen-induced T cell and B cell proliferation as well as proliferation induced by several cytokines, including IL-2, IL-3, IL-4 and IL-6 (reviewed by Sehgal et al., Med. Research Rev.14: 1-22, 1994). It can also inhibit antibody production. Rapamycin has been shown to block the cytokine-induced activation of p70S6 kinase which appears to correlate with Rapamycin""s ability to decrease protein synthesis accompanying cell cycle progression (Calvo et al., Proc. Natl. Acad. Sci. USA, 89:7571-7575, 1992; Chung et al., Cell 69:1227-1236, 1992; Kuo et al., Nature 358:70-73, 1992; Price et al., Science 257:973-977, 1992). It also inhibits the activation of cdk2/cyclin E complex (Flanagan et al., Ann. N.Y.Acad. Sci, 30;696:31-37, 1993 Flanagan et al., J.Cell Biochem. 17A:292, 1993). Rapamycin""s effects are not mediated by direct binding to p70s6 kinase and cdk2/cyclin E, but by action of the Rapamycin-FKBP complex on upstream component(s) which regulate the activation status of the kinases.
It is generally accepted that the action of immunosuppressive drugs, such as Rapamycin, cyclosporine and FK506, is dependent upon the formation of a complex with their respective intracellular receptor proteins called immunophilins. While the binding of these immunosuppressants with their respective immunophilins inhibits the cis-trans peptidyl prolyl isomerase (PPIase) activity of immunophilins, PPIase inhibition is not sufficient to mediate the immunosuppressive activity (reviewed in Armistead and Harding, Annual Reports in Med. Chem, 28:207-215:1993). Two rapamycin analogs which are Diels Alder adducts, one with 4-phenyl-1,2,4-triazoline-3,5-dione, and the second with 4-methyl-1,2,4-triazoline-3,5-dione, bind to FKBP, inhibited its PPIase activity, yet they did not exhibit any detectable immunosuppressive activity. The phenyl-triazolinedione Diels Alder adduct at high molar excess has been shown to competitively inhibit rapamycin""s effect on DNA synthesis in mitogen-stimulated stimulated murine thymocyte proliferation (Ocain et al., Biochem. Biophys. Res. Commun. 192:1340, 1993). Recent evidence suggests that the binary immunophilin-drug complex such as cyclophilin-cyclosporin A and FKBP-FK506 gains a new function that enables it to block signal transduction by acting on specific target proteins. The molecular target of both cyclophilin-cyclosporin A and FKBP-FK506 complexes such as has been identified as the Ca+2/calmodulin dependent serine/threonine phosphatase calcineurin (J. Liu et al, Cell 66, 807, 1991; J. Liu et al, Biochemistry 31, 3896, 1992; W. M. Flanagan, et al., Nature 352, 803, 1992; McCaffrey et al., J. Biol. Chem. 268, 3747, 1993; McCaffrey et al., Science 262:750, 1993).
Rapamycin""s antifungal and immunosuppressive activities are mediated via a complex consisting of Rapamycin, a member of the FK506 binding protein (FKBP) family and at least one additional third protein, called the target of Rapamycin (TOR). The family of FKBPs is reviewed by Armistead and Harding (Annual Reports in Med. Chem, 28:207-215:1993). The relevant FKBP molecule in Rapamycin""s antifungal activity has been shown to be FKBP12 (Heitman et al., Science 253:905-909:1993). In mammalian cells, the relevant FKBPs are being investigated. Although two TOR proteins (TOR1 and TOR2) have been identified in yeast (Kunz et al., Cell 73:585-596:1993), the target of Rapamycin in human cells remains elusive. The carboxy terminus of yeast TOR2 has been shown to exhibit 20% identity with two proteins, the p110 subunit of phosphatidylinositol 3-kinase and VPS34, a yeast vacuolar sorting protein also shown to have PI 3K activity. However, J. Blenis et al. (Joint Meeting of the American Association of Immunologists and The Clinical Immunology Society, Denver, Colo., May, 1993) have reported that Rapamycin-FKBP12 complex does not directly mediate its effects on PDGF stimulated cells via the p110, p85 PI 3K complex.
This invention concerns isolated, cloned and expressed proteins which bind to a complex of GST-FKBP12-Rapamycin. These proteins are isolated from membrane preparations of Molt 4 T cell leukemia. The sizes of the four novel proteins are estimated by PAGE migration to be 125xc2x112 kilodaltons (kDa), 148xc2x114 kDa, 208xc2x115 kDa and 210xc2x120 kDa and will be referred to herein and in the claims that follow, as the 125 kDa, 148 kDa, 208 kDa, and 210 kDa, respectively. The four proteins may also be referred to herein as effector proteins.
The proteins of this invention can be used in screening assays, such as enzyme inhibitor assays and binding assays, to identify endogenous complexes and ligands and novel exogenous compounds (like Rapamycin) which modulate their functions. They can also be used in assays to identify compounds with therapeutic benefit for restenosis, immunomodulation and as antitumor agents. Cloning the proteins of this invention does not only allow the production of large quantities of the proteins, it also provides a basis for the development of related anti-sense therapeutics. The use of cDNA clones to generate anti-sense therapeutics with immunomodulatory activity (for use against transplantation rejection, graft versus host disease, autoimmune diseases such as lupus, myasthenia gravis, multiple sclerosis, rheumatoid arthritis, type I diabetes, and diseases of inflammation such as psoriasis, dermitis, eczema, seborrhea, inflammatory bowel disease, pulmonary inflammation, asthma, and eye uveitis), antirestenosis and anti-tumor activity is included within the scope of this invention.
The proteins of the present invention can be isolated from mammalian cells, such as cells of the T cell leukemia cell line, Molt 4 (ATCC 1582, American Type Cell Culture, 12301 Parklawn Drive, Rockville, Md., USA, 20852), the B cell lymphoma, BJAB, or normal human T cells. These mammalian cells can be lysed in a buffer containing protease inhibitors and reducing agent (2-ME), such as hypotonic buffer A (100 mM HEPES, pH 7.5, 20 mM KCl, 1 mM EDTA, 0.4 mM PMSF and 2 mM beta mercaptoethanol (2-ME)). The cell nuclei and unbroken cells are cleared by centrifugation at a temperature which minimizes protein degradation. The membrane fraction of the cells can then be concentrated or pelleted by ultracentrifugation at 100,000 g. Detergent solubilization of the membrane pellet is carried out in a detergent containing buffer such as buffer B (50 mM Tris, pH 7.2, 100 mM NaCl, 20 mM KCl, 0.2 mM PMSF, 1 mM 2-ME, 2 mM CaCl2, 2 mM MgCl2, 5 xcexcg/ml aprotinin, leupeptin, pepstatin A and antipain), containing CHAPSO (3-[(3-cholamido-propyl)dimethylammonio]-1-propane sulfonate; 12 mM) or Tritonxc3x97100 (polyethylene glycol 4-isooctylphenyl ether). The solubilized membrane proteins can then be separated from the debris by 1,000,000 g ultracentrifugation at a temperature which minimizes protein degradation. The supernatant containing solubilized membrane proteins is then preabsorbed with an affinity resin, such as glutathione resin, in the presence of protease inhibitors at a temperature which minimizes protein degradation. After centrifugation to remove the resin from the supernatant, the supernatant is then incubated with complexed Rapamycin or Rapamycin analog to FKBP, such as GST-FKBP12-Rapamycin at a temperature which minimizes protein degradation. The mixture of solubilized membrane proteins, incubated with complexed Rapamycin or Rapamycin analog to FKBP, such as GST-FKBP12-Rapamycin, can then be incubated with the affinity resin to bind the complexes of rapamycin or rapamycin analog, FKBP fusion protein and binding proteins at a temperature which minimizes protein degradation. After most non-specific proteins are rinsed away using a detergent containing buffer, such as Buffer C (50 mM Tris, pH 7.2, 100 mM NaCl, 20 mM KCl, 0.2 mM PMSF, 1 mM 2-ME or 10 mM dithiothreitol, 0-5 mM CaCl2, 0-5 mM MgCl2, 5 xcexcg/ml aprotinin, leupeptin, pepstatin A and antipain and 0.1% Tritonxc3x97100) (Polyethylene glycol 4-isooctyl phenyl ether), the proteins are eluted from the resin under denaturing conditions, such as a buffer containing sufficient detergent to dissociate it from resin (e.g. Laemli buffer with or without glycerol or dye, as described by Laemli, Nature 227:680, 1970), or non-denaturing conditions such as a buffer containing an appropriate eluting compound for the affinity column, such as 5 mM glutathione. The proteins can then be separated by size using SDS polyacrylamide gel electrophoresis (SDS-PAGE).
The present invention also includes the genomic DNA sequences for the abovementioned proteins, as well as the cDNA and anti-sense RNA and DNA sequences which correspond to the genes for the abovementioned proteins. The present invention further includes the proteins of other mammalian species which are homologous or equivalent at least in function to the abovementioned proteins, as well as the DNA gene sequences for the homologous or equivalent proteins and the cDNA and anti-sense RNA and DNA sequences which correspond to the genes for the homologous or equivalent proteins.
For the purposes of this disclosure and the claims that follow, equivalents of the proteins of this invention are considered to be proteins, protein fragments and/or truncated forms with substantially similar, but not identical, amino acid sequences to the proteins mentioned above, the equivalents exhibiting rapamycin-FKBP complex binding characteristics and function similar to the proteins mentioned above. Therefore, in this specification and the claims below, references to the 125 kDa, 148 kDa, 208 kDa, and 210 kDa proteins of this invention are also to be understood to indicate and encompass homologous or equivalent proteins, as well as fragmented and/or truncated forms with substantially similar, but not identical, amino acid sequences of the 125 kDa, 148 kDa, 208 kDa, and 210 kDa proteins mentioned above.
These proteins or protein homologues or equivalents can be generated by similar isolation procedures from different cell types and/or by recombinant DNA methods and may be modified by techniques including site directed mutagenesis. For example, the genes of this invention can be engineered to express one or all of the proteins as a fusion protein with the fusion partner giving an advantage in isolation (e.g. HIS oligomer, immunoglobulin Fc, glutathione S-transferase, FLAG etc). Mutations or truncations which result in a soluble form can also be generated by site directed mutagenesis and would give advantages in isolation.
This invention further includes oligopeptide fragments, truncated forms and protein fragments that retain binding affinity yet have less than the active protein""s amino acid sequences. This invention also includes monoclonal and polyclonal antibodies specific for the proteins and their uses. Such uses include methods for screening for novel agents for immunomodulation and/or anti-tumor activity and methods of measuring the parent compound and/or metabolites in biological samples obtained from individuals taking immunosuppressive drugs. The use of the cDNA clone to generate anti-sense therapeutics (Milligan et al, J. Med. Chem. 36:1923-1936, 1993) with immunomodulatory activity (transplantation rejection, graft versus host disease, autoimmune diseases such as lupus, myasthenia gravis, multiple sclerosis, rheumatoid arthritis, type I diabetes, and diseases of inflammmation such as psoriasis, dermitis, eczema, seborrhea, inflammatory bowel disease, pulmonary inflammation, asthma, and eye uveitis), and anti-tumor activity is also included in the present invention.
The proteins of this invention can also be made by recombinant DNA techniques familiar to those skilled in the art. That is, the gene of the protein in question can be cloned by obtaining a partial amino acid sequence by digestion of the protein with a protease, such as Lysine C, and isolating the resulting protein fragments by microbore HPLC, followed by fragment sequencing (Matsudaira in A Practical Guide to Protein and Peptide Purification for Microsequencing, Academic Press (San Diego, Calif., 1989)). The determined sequence can then be used to make oligonucleotide probes which can be used to screen a human cDNA library directly or generate probes by polymerase chain reaction. The library can be generated from human T cells or the cell lines, Molt 4, Jurkat, or other etc. to obtain clones. These clones can be used to identify additional clones containing additional sequences until the protein""s full gene, i.e. complete open reading frame, is cloned.
It is known in the art that some proteins can be encoded by an open reading frame which is longer than initially predicted by the size of the protein. These proteins may represent cleavage products of the precursor protein translated from the complete open reading frame (eg. IL-1 beta) or proteins translated using a downstream start codon (eg. Hepaptitis B surface antigen). In view of this knowledge, it is understood that the term cDNA as used herein and in the claims below refers to cDNA for the gene""s complete open reading frame or any portions thereof which may code for a protein of this invention or the protein""s fragments, together or separate, or truncated forms, as previously discussed.
In a complementary strategy, the gene(s) for the proteins of this invention may be identified by interactive yeast cloning techniques using FKBP12:RAPA as a trap for cloning. These strategies can also be combined to quicken the identification of the clones.
The relevant cDNA clone encoding the gene for any of the four proteins can also be expressed in E. coli, yeast, or baculovirus infected cells or mammalian cells using state of the art expression vectors. Isolation can be performed as above or the cDNA can be made as a fusion protein with the fusion partner giving an advantage in isolation (e.g. HIS oligomer, immunoglobulin Fc, glutathione S-transferase, etc). Mutations which result in a soluble form can also be generated by site directed mutagenesis and would give advantages in isolation.
The uses of such cDNA clones include production of recombinant proteins. Further, such recombinant proteins, or the corresponding natural proteins isolated from mammalian cells, or fragments thereof (including peptide oligomers) are useful in generation of antibodies to these proteins. Briefly, monoclonal or polyclonal antibodies are induced by immunization with recombinant proteins, or the corresponding natural proteins isolated from mammalian cells, or fragments thereof (including peptide oligomers conjugated to a carrier protein (e.g. keyhole limpet hemocyanin or bovine serum albumin)) of animals using state of the art techniques. The antibodies can be used in the purification process of the natural proteins isolated from mammalian cells or recombinant proteins from E. coli, yeast, or baculovirus infected cells or mammalian cells, or cell products.
The uses of such cDNA clones include production of recombinant proteins. Further, such recombinant proteins, or the corresponding natural proteins isolated from mammalian cells, are useful in methods of screening for novel agents such as synthetic compounds, natural products, exogenous or endogenous substrates for immunomodulation and/or antitumor activity. The natural products which may be screened may include, but are not limited to, cell lysates, cell supernatants, plant extracts and the natural broths of fungi or bacteria. As an example of a competitive binding assay, one of these proteins attached to a matrix (either covalently or noncovalently) can be incubated with a buffer containing the compounds, natural products, cell lysates or cell supernatants and a labeled rapamycin:FKBP complex. The ability of the compound, natural products, exogenous or endogenous substrates to competitively inhibit the binding of the complex or specific antibody can be assessed. Examples of methods for labeling the complex include radiolabeling, fluorescent or chemiluminescent tags, fusion proteins with FKBP such as luciferase, and conjugation to enzymes such as horse radish peroxidase, alkaline phosphatase, acetylcholine esterase (ACHE), etc. As an example of an enzymatic assay, the proteins are incubated in the presence or absence of novel agents such as synthetic compounds, natural products, exogenous or endogenous substrates with substrate and the enzymatic activity of the protein can be assessed. Methods of measuring the parent compound and/or metabolites in biological samples obtained from individuals taking immunosuppressive drugs can also be assessed using these proteins.
This invention includes a method for identifying substances which may be useful as immunomodulatory agents or anti-tumor agents, the method utilizing the following steps:
a) combining the substance to be tested with one of the four mammalian proteins (125 kDa, 148 kDa, 208 kDa or 210 kDa) of this invention, with the protein being bound to a solid support:
b) maintaining the substance to be tested and the protein bound to the solid support of step (a) under conditions appropriate for binding of the substance to be tested with the protein, and
c) determining whether binding of the substance to be tested occurred in step (b).
This invention also includes a method for identifying substances which may be useful as immunomodulatory or anti-tumor agents which involves the following steps:
a) combining a substance to be tested with one of the mammalian proteins of this invention, the protein being bound to a solid support:
b) maintaining the substance to be tested and the protein bound to the solid support of step (a) under conditions appropriate for binding of the substance to be tested with the protein, and
c) determining whether the presence of the substance to be tested modulated the activity of the mammalian protein.
This invention further includes a method for detecting, in a biological sample, rapamycin, rapamycin analogs or rapamycin metabolites which, when complexed with a FKBP, bind to one of the four listed proteins of this invention, the method comprising the steps of:
a) combining the biological sample with a FKBP to form a first mixture containing, if rapamycin, rapamycin analogs or rapamycin metabolites are present in the biological sample, a rapamycin:FKBP complexes, rapamycin analog:FKBP complexes, or rapamycin metabolite:FKBP complexes;
b) creating a second mixture by adding the first mixture to one of the proteins of this invention, the protein bound to a solid support;
c) maintaining the second mixture of step (b) under conditions appropriate for binding the rapamycin:FKBP complexes, rapamycin analog:FKBP complexes, or rapamycin metabolite:FKBP complexes, if present, to the protein of this invention; and
d) determining whether binding of the rapamycin:FKBP complexes, rapamycin analog:FKBP complexes, or rapamycin metabolite:FKBP complexes and the protein occurred in step (c).
Also included in this invention is the use of the cDNA clones to generate anti-sense therapeutics. This can be accomplished by using state of the art techniques, such as those described in Milligan et al, J. Med. Chem. 36:14:1924-1936, 1993. For the purposes of this disclosure and the claims that follow, antisense RNA and DNA are understood to include those RNA and DNA strands derived from a cDNA clone which encodes for one of the four proteins (125 kDa, 148 kDa, 208 kDa or 210 kDa) of the present invention which have a native backbone or those which utilize a modified backbone. Such modifications of the RNA and DNA backbones are described in Milligan et al, J. Med. Chem. 36:14:1924-1936, 1993. The antisense compounds created by the state of the art techniques recently described (Milligan et al, J. Med. Chem. 36:14:1924-1936, 1993) can be useful in modulating the immune response and thus useful in the treatment or inhibition of transplantation rejection such as kidney, heart, liver, lung, bone marrow, pancreas (islet cells), cornea, small bowel, and skin allografts, and heart valve xenografts; in the treatment or inhibition of autoimmune diseases such as lupus, rheumatoid arthritis, diabetes mellitus, myasthenia gravis, and multiple sclerosis; and diseases of inflammation such as psoriasis, dermatitis, eczema, seborrhea, inflammatory bowel disease, and eye uveitis. The antisense molecules of this invention can have antitumor, antifungal activities, and antiproliferative activities. The compounds of this invention therefore can be also useful in treating solid tumors, adult T-cell leukemia/lymphoma, fungal infections, and hyperproliferative vascular diseases such as restenosis and atherosclerosis. Thus, the present invention also comprises methods for treating the abovementioned maladies and conditions in mammals, preferably in humans. The method comprises administering to a mammal in need thereof an effective amount of the relevant antisense therapeutic agent of this invention.
When administered for the treatment or inhibition of the above disease states, the antisense molecules of this invention can be administered to a mammal orally, parenterally, intranasally, intrabronchially, transdermally, topically, intravaginally, or rectally.
It is contemplated that when the antisense molecules of this invention are used as an immunosuppressive or antiinflammatory agent, they can be administered in conjunction with one or more other immunoregulatory agents. Such other immunoregulatory agents include, but are not limited to azathioprine, corticosteroids, such as prednisone and methylprednisolone, cyclophosphamide, rapamycin, cyclosporin A, FK-506, OKT-3, and ATG. By combining the complexes of this invention with such other drugs or agents for inducing immunosuppression or treating inflammatory conditions, the lesser amounts of each of the agents are required to achieve the desired effect. The basis for such combination therapy was established by Stepkowski whose results showed that the use of a combination of rapamycin and cyclosporin A at subtherapeutic doses significantly prolonged heart allograft survival time. [Transplantation Proc. 23: 507 (1991)].
Treatment with these antisense compounds will generally be initiated with small dosages less than the optimum dose of the compound. Thereafter the dosage is increased until the optimum effect under the circumstances is reached. Precise dosages will be determined by the administering physician based on experience with the individual subject treated. In general, the antisense compounds of this invention are most desirably administered at a concentration that will afford effective results without causing any harmful or deleterious side effects.
In light of the therapeutic value of the abovementioned antisense compounds, this invention also includes pharmaceutical compositions containing the antisense RNA and antisense DNA compounds derived from cDNA clones which encode for the 125 kDa, 148 kDa, 208 kDa and 210 kDa proteins of this invention.
This invention also comprises the following process for isolating the proteins of this invention, as well as the proteins isolated therefrom:
A process for isolating proteins from mammalian cells, the process comprising the steps of:
1. The mammalian cells of interest are grown and harvested. As mentioned previously, the cells may be of T cell origin (e.g. T cell lymphomas, leukemias, normal human T cells), B cell origin (e.g. EBV transformed B cells, normal human B cells), mast cells, or other cell sources sensitive to rapamycin. The cells may be processed shortly after harvesting or may be stored frozen, such as in pellets, prior to processing. The cells which are kept frozen may be stored in a dry ice and ethanol bath, stored frozen at xe2x88x9270-80xc2x0 C. until use. This step of growing and harvesting the cells of interest may be seen as the first step of this process or as merely preparatory for the present process.
2. Cells are lysed in a buffer containing a buffering agent (e.g.HEPES, Tris, pH 7.5), low salt (e.g.10-50 mM NaCl or KCl), chelating agent (e.g. 1-2 mM EDTA), protease inhibitors (e.g.0.4 mM PMSF) and a reducing agent (e.g. 2 mM 2-ME or 1-20 mM Dithiothreitol) at a temperature which minimizes protein degradation (e.g. 4xc2x0 C.). It should be understood that the mammalian cells may be treated in any manner capable of producing cell lysis, including sonic lysis and douncing.
3. Unbroken cells and cell nuclei are precleared from lysates by centrifugation at a temperature which minimizes protein degradation (e.g. 4xc2x0 C.). Centrifugation at, for example, 1600 g for 10 minutes has been found sufficient to preclear the unbroken cells and cell nuclei from the lysates. This step, while not mandatory, provides a clearer preparation for the steps that follow.
4. The membrane fraction in the precleared lysate is then concentrated, such as by ultracentrifugation. An example of this concentration would be ultracentrifugation at 100,000 g for 1-1.5 hours.
5. The membrane proteins (e.g. transmembrane, integral and membrane associated proteins) are then solubilized. This may be accomplished by incubating the pellet of Step 4 in a buffer containing a detergent which solubilizes the proteins without detrimentally denaturing them, a buffering agent (e.g. 20-50 mM Tris or HEPES, pH 7.2), salt (e.g. 100-200 mM NaCl+20 mM KCl), reducing agent (e.g. 1-2 mM 2-ME or 1-20 mM dithiothreitol), protease inhibitors (e.g. 0.2 mM PMSF, 5 xcexcg/ml aprotinin, leupeptin, pepstatin A and antipain), divalent cations (e.g. 0-5 mM CaCl2, 0-5 mM MgCl2) at a temperature which minimizes protein degradation (e.g. 4xc2x0 C.). Examples of detergents useful in this step are CHAPSO (3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate) or Tritonxc3x97100 (polyethylene glycol 4-isooctylphenyl ether). After this step, the mixture contains solubilized membrane proteins and non-solubilized cellular debris.
6. The solubilized membrane proteins are separated from the non-solubilized cellular debris, such as by ultracentrifugation (eg 100,000 for 1-1.5 hours) at a temperature which minimizes protein degradation (e.g. 4xc2x0 C.).
7. The supernatant containing solubilized membrane proteins is incubated with an affinity resin in a buffer containing a buffering agent (e.g.20-50 mM Tris or HEPES, pH 7.2), salt (e.g. 100-200 mM NaCl+20 mM KCl), reducing agent (e.g. 1-2 mM 2-ME or 10-20 mM dithiothreitol), protease inhibitors (e.g. 0.2 mM PMSF, 5 xcexcg/ml aprotinin, leupeptin, pepstatin A and antipain), divalent cations (e.g. 0-5 mM CaCl2, 0-5 mM MgCl2) at a temperature and time which allows the absorption of the proteins which bind to affinity resin directly, and minimizes protein degradation (e.g. 4xc2x0 C.).
8. The resin is then removed from the supernatant by centrifugation at a temperature which minimizes protein degradation (e.g. 4xc2x0 C.).
9. The supernatant is then incubated with Rapamycin or Rapamycin analog (IC50 in LAF less than 500 nM) complexed to fusion protein of FKBP12+protein which enhances the isolation of the desired effector protein and through which the fusion protein binds to an affinity resin or affinity column, such as GST-FKBP12, Histidine oligomer-FKBP12, biotin-FKBP12, etc., in a buffer containing a buffering agent (e.g. 20-50 mM Tris or HEPES, pH 7.2), salt (e.g. 100-200 mM NaCl+20 mM KCl), reducing agent (e.g. 1-2 mM 2-ME or 1-20 mM dithiothreitol), protease inhibitors (e.g. 0.2 mM PMSF, 5 xcexcg/ml aprotinin, leupeptin, pepstatin A and antipain), divalent cations (e.g. 0-5 mM CaCl2, 0-5 mM MgCl2) at a temperature and for a time which allows binding of the effector proteins to the fusion FKBP protein:Rapamycin or analog complexes and minimizes protein degradation (e.g. 4xc2x0 C. and 1-2 hours).
10. The mixture of Step 9 containing the effector proteins and fusion FKBP protein:Rapamycin complexes is incubated with an affinity resin at a temperature and for a time which allows binding of the complexes of the effector proteins and fusion FKBP protein:Rapamycin or analog to the affinity resin and minimizes protein degradation (e.g. 4xc2x0 C. and 0.5-2 hours).
11. Most non-specific proteins are rinsed away from the resin using a buffer which dissociates binding of non-specific proteins but not the complex between the desired proteins and RAPA-FKBP, such as a buffer containing a buffering agent (e.g.20-50 mM Tris or HEPES, pH 7.2), salts (e.g. 100-1000 mM NaCl, KCl), reducing agent (e.g. 1-2 mM 2-ME or 10-20 mM dithiothreitol), protease inhibitors (e.g. 0.2 mM PMSF, 5xcexcg/ml aprotinin, leupeptin, pepstatin A and antipain), divalent cations (e.g. 0-5 mM CaCl2, 0-5 mM MgCl2) and detergent which dissociates binding of non-specific proteins but not the complex between the four proteins and RAPA-fusion FKBP protein such as Tritonxc3x97100 (Polyethylene glycol 4-isooctyl phenyl ether).
12. The effector proteins and the fusion FKBP protein:Rapamycin complexes are eluted from the resin using an appropriate buffer, such as a buffer containing sufficient detergent to dissociate it from resin (e.g. Laemli buffer with or without glycerol or dye, Laemli, Nature 227:680, 1970), or an appropriate eluting compound for the affinity column, such as glutathione, histidine.
13. The effector proteins can then be separated by size. This may be accomplished in any manner which separates the proteins by size, including, but not limited to, polyacrylamide gel electrophoresis and size exclusion column chromatography.
It might also be useful to compare the proteins isolated by a control procedure, that is a procedure which substitutes buffer for the rapamycin or rapamycin analog with an IC50 in LAF less than 500 nM in step 8, can be used to more easily distinguish proteins which bind to the rapamycin:FKBP complex.
The proteins of this invention can also be made by recombinant DNA techniques familiar to those skilled in the art. That is, the gene of the protein in question can be cloned by obtaining a partial amino acid sequence by digestion of the protein with an appropriate endopeptidase, such as Lysine C, and isolating the resulting protein fragments by microbore HPLC, followed by fragment sequencing (Matsudaira in A Practical Guide to Protein and Peptide Purification for Microsequencing, Academic Press, San Diego, Calif. 1989). The determined sequence can then be used to make oligonucleotide probes which can be used to screen a human cDNA library, such as those for human T cells, Molt 4, Jurkat, etc, to obtain clones. (Sambrook, Fritsch, and Maniatas, Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Press, 1989) These clones can be used to identify additional clones containing additional sequences until the protein""s full gene is cloned (Sambrook, Fritsch, and Maniatas, Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Press, 1989). In a complementary strategy, the gene(s) may be identified by interactive yeast cloning techniques using FKBP12:RAPA as a trap for cloning (Chien et al., Proc. Natl. Acad. Sci. 88: 9578-9582, 1991). These strategies can also be combined to quicken the identification of the clones.
The relevant cDNA clone can also be expressed in E. coli, yeast, or baculovirus infected cells or mammalian cells using state of the art expression vectors. Isolation can be performed as above or the cDNA can be made as a fusion protein with the fusion partner giving an advantage in isolation (e.g. HIS oligomer, immunoglobulin Fc, glutathione S-transferase, etc). Mutations which result in a soluble form can also be generated by site directed mutagenesis and would give advantages in isolation.
Homologs in the mouse, rat, monkey, dog and other mammalian species can be obtained using similar procedures. In addition, upon isolation of the human clone of the proteins, the clone can be used to screen for homologs in other mammalian species. These homologs can also be used to develop binding assays and to set up high through put screening assays for compounds, endogenous ligands, exogenous ligands with immunomodulatory activity.
Compounds, endogenous ligands and exogenous ligands having such immunomodulatory activity would can be useful in modulating the immune response and thus useful in the treatment or inhibition of transplantation rejection such as kidney, heart, liver, lung, bone marrow, pancreas (islet cells), cornea, small bowel, and skin allografts, and heart valve xenografts; in the treatment or inhibition of autoimmune diseases such as lupus, rheumatoid arthritis, diabetes mellitus, myasthenia gravis, and multiple sclerosis; and diseases of inflammation such as psoriasis, dermatitis, eczema, seborrhea, inflammatory bowel disease, and eye uveitis.
The compounds, endogenous ligands and exogenous ligands mentioned above can also have antitumor, antifungal activities, and antiproliferative activities. The compounds of this invention therefore can be also useful in treating solid tumors, adult T-cell leukemia/lymphoma, fungal infections, and hyperproliferative vascular diseases such as restenosis and atherosclerosis.